1. Field of the Invention
The present invention relates to a UV-curable optical resin adhesive composition, which is used in a display structure including a protective cover plate and an image display panel being stacked and bonded together, for filling a gap therebetween, and imparts excellent image display quality, transparency, adhesion reliability, and durability to the display structure while keeping luminosity and high contrast of the display structure. Such UV-curable optical resin adhesive composition can be suitable for reworking (repairing) the display structure.
2. Description of the Related Art
In recent years, along with evolution of the advanced information society, many functional devices have been proposed including image display panels such as an organic electroluminescence (EL) display device, and a liquid crystal display device, various electronic devices for display such as an electrophoretic display device, optical devices such as an organic EL illumination device, an optical element, and an optical waveguide, and solar cells such as a thin film silicon solar cell, an organic thin film solar cell, and a dye-sensitized solar cell.
Particularly in the liquid crystal display devices, in recent years, there is a tendency to be enlarged in size and screen, such as, for example, wide-screen HD TVs and 3-D TVs. In those liquid crystal display devices, a structure called an air-gap structure (hollow structure) with a gap of approximately 0.5 to 1.5 mm has been conventionally adopted and formed between a liquid crystal display (LCD) panel (LCD module) and a protective cover plate (front cover made of glass, an acrylic resin, or the like) to protect the surface of the LCD panel as well as to act as a polarizing plate (see Japanese Patent Application Laid-open No. 2009-8851). However, with respect to the refractive index of the air in the above-mentioned air gap structure portion, a combination of the LCD panel (LCD module) and the protective cover plate (front cover) with various polarizing plates has a refractive index of approximately 1.5. Thus, generally, luminance and contrast are inevitably decreased due to diffusion or scattering of image light in the panel, which is emitted from the LCD module, reflection of outside light such as sunlight, and the like. Therefore, the resulting images are not always satisfied, and hence image display with higher quality has been demanded.
For this reason, it is suggested to fill a transparent optical resin having a refractive index close to that of glass or an acrylic resin into the above-mentioned air gap structure portion (see, for example, Japanese Patent Application Laid-open No. 2008-281997). Thus, the above-mentioned air gap is filled with the optical resin to eliminate the optical interface between the LCD panel (LCD module) and the protective cover plate (front cover). This leads to a reduction in reflection/diffusion of image light, and the reduction largely contributes to improvements in luminance and contrast. As a result, high quality images can be now provided. Further, the strength of the entire image display device can be increased by filling the above-mentioned air gap with the optical resin. In other words, glass, which is a formation material, can be prevented from being scattered even if the protective cover plate (front cover) is broken, while an improvement in strength of the image display device can be simultaneously attained.